Ensuring required collimator settings

1. LHC Machine ProtectionSystem ReviewOliver Aberle 13 April 2005with input from R. Assmann and R. Losito Ensuring required collimator settings

2. Overview • Design features • Movements • Position control • Electronics, control and interlocks • Summary LHC Machine Protection System Review

3. Design features Three major design criteria to assure a precise jaw position: • Tight tolerances andadapted material choice • Movement with smallstep size • Independent positionmeasurement Courtesy of A. Bertarelli and R. Perret LHC Machine Protection System Review

4. Design features Side view at one end Vacuumtank Temperaturesensor Microphonic sensor Reference Reference Motor Motor Resolver Gap opening (LVDT) + switches for IN, OUT,ANTI-COLLISION Gap position (LVDT) Resolver LHC Machine Protection System Review

5. Design features • Two opposite jaws per collimator provides enhanced safety for settings if compared to TEVATRON and RHIC! • Position and angle control for jaws.Automatic retraction and play elimination. • Independent position read back and end position switches. • Independent & direct monitoring of thecollimator gap. • Survey of temperature, vacuum and shock impact. LHC Machine Protection System Review

6. Movements Collimators will be moved by Stepper motors: • δL is defined by the geometry of the motor • That makes “easy” to implement a given ∆L • The movement can be implemented in open loop position:- sensors are not necessarily needed- the system is more robust. • After a power-cut, or single-event, we need to reset the step counter to a home position LHC Machine Protection System Review

7. Movements We use • 2-phase hybrid motors, 200 step/revolution • Angle resolution 1.8°±0.1° • 2mm pitch lead screw • Pull-out torque sufficiently higher than load And we have: • 2mm/200 step = (10 ±0.5) µm !!!! • Static Error due to load negligible if • pull-out torque >> load torque • With Ministep Driver we can do 400, 800, 1600, steps/revolution (5, 2.5, 1.25, 0.75 µm) LHC Machine Protection System Review

8. Position controls LVDT and Resolvers: Radiation hardness:If the motor survives, the LVDT and the Resolvers can survive. Lifetime:“infinite” since contact less (no mechanical stresses).Resolution is determined by ADC in conditioning electronics.16 bits on ±40 mm= 1.2µm resolution LHC Machine Protection System Review

9. Electronics, control and interlock LHC Machine Protection System Review

10. Interface to interlock system • Preliminary thinking. Details being worked out. • Collimation control system has several paths to interlock system. Beam dump could be requested if: • Jaw temperatures exceed tolerance, abnormal motor and/or sensor status, shock beam impact detected, …. • In, out or anti-collision switches are activated. • Jaw positions and/or gap deviate from requested value for the considered time (setting function). Depends on tolerance. Monitor with 40 mm accuracy. • Inconsistency detected between: • requested settings and machine mode, energy, … (to be defined). • among requested settings (e.g. protection gaps < cleaning gaps). • measured orbit and collimator reference orbit (or track orbit with coll.?) • Crucial connection to interlock system: Collimator design and extensive monitoring should prevent “wrong” and “unsafe” settings! Increasing complexity LHC Machine Protection System Review

11. Summary • Two jaws per collimator provide important enhancement for safety of collimator setting control. • Very tight mechanical tolerances and play minimization with spring system. • Stepping motor for precise positioning. • Two additional, independent devices for direct measurement of jaw positions and collimator gap (redundancy). • Several possible links to interlock system from low through high level controls  control system being attacked now. • We feel confident that jaw positions and gaps can be controlled by hardware to significantly better than 100 mm during all times (~ 40 mm). LHC Machine Protection System Review